The present invention relates to a discharge lamp lighting device and a lighting system.
Generally speaking, when a discharge lamp is close to the end of its life, it causes a half-wave discharge, which is an abnormal discharge that generates abnormal heat in the regions around the electrodes. This causes a particularly serious problem in case of a discharge lamp having a slender glass bulb. As the distance between the glass bulb of a slender-type lamp and each one of the electrodes that are contained in the glass bulb is minimal, such an abnormal discharge tends to increase the temperature of the glass bulb excessively, sometimes resulting in melting of the glass bulb, the plastic bases attached to the glass bulb, and the sockets on which the plastic bases are mounted.
Melting of this type may be prevented by various means; for example, when an abnormality such as reaching the end of life, is detected in a discharge lamp the function of a high frequency generating means that serves to light the discharge lamp may be halted.
However, stopping the function of the high frequency generating means causes the discharge lamp to become dark.
An example of conventionally known structure that are capable of preventing a discharge lamp from becoming dark when an abnormality is detected is disclosed in Japanese Patent Provisional Publication No. 231295-1989. The discharge lamp lighting device disclosed in said Japanese Patent Provisional Publication No. 231295-1989 calls for connecting a plurality of discharge lamps in parallel with one another and, upon detecting an abnormality such as coming to the end of life in one or more discharge lamps when said plurality of discharge lamps are lit, reducing the output from the high frequency generating means to such a level that the other lamps, which are operating in normal conditions, can remain lit. In other words, if there is any discharge lamp that has reached the end of its life, the other discharge lamps are kept lit in the state where the output from the high frequency generating means is reduced. Thus, the minimum necessary luminance level is ensured.
However, should the discharge lamp lighting device disclosed in Japanese Patent Provisional Publication No. 231295-1989 be applied to slender-type discharge lamps, wherein the distance between the glass bulb and each electrode of each lamp is minimal, the temperature of the glass bulb of an abnormal lamp would be still too high in spite of the reduced output from the high frequency generating means.
Furthermore, the structure described above calls for reducing the output to such a level as to prevent the discharge lamps in the abnormal condition from continuing the discharge. Doing thus, however, makes it difficult to keep the normal discharge lamps lit. In case there is an abnormal lamp in a household lighting fixture, which is normally designed such that a single high frequency generating means lights two or more discharge lamps having different rated power, it is particularly difficult to keep the other discharge lamps, which are in the normal conditions, lit.
In order to solve the above problems, an object of the present invention is to provide a discharge lamp lighting device and a lighting system that are capable of lighting discharge lamps in an appropriate condition and maintaining them so they are appropriately lit.
The invention includes a load circuit having a discharge lamp, an inductance and a capacitance; and a combination-type high frequency inverter having a full-wave rectifier for rectifying a low frequency AC voltage without smoothing the voltage, an inductor, a smoothing condenser, a resonance condenser and at least a pair of switching means which have a function of an antiparallel diode and are adapted to be alternately switched and respectively take part in charging the smoothing condenser and discharge from the smoothing condenser, said combination-type high frequency inverter adapted to operate in such a manner that the xe2x80x98onxe2x80x99 duration of the switching means that is adapted to take part in charging the smoothing condenser is variable, while the xe2x80x98onxe2x80x99 duration of the switching means that is adapted to take part in discharge from the smoothing condenser is fixed, and the combination-type high frequency inverter having a function of an active filter and serving to energize the load circuit with a high frequency output.
By operating the combination-type high frequency inverter with the xe2x80x98onxe2x80x99 duration of the switching means that is adapted to take part in charging the smoothing condenser being variable and the xe2x80x98onxe2x80x99 duration of the switching means that is adapted to take part in discharge from the smoothing condenser being fixed, the charge voltage on the smoothing condenser can be adjusted so that the high frequency output voltage and, consequently, the load characteristics are changed as desired. The invention described above is thus capable of easily giving a discharge lamp load characteristics that are optimal for the current mode in accordance with whether the discharge lamp is in the start-up mode or luminance mode. Furthermore, by making the xe2x80x98onxe2x80x99 duration of the switching means that is adapted to take part in charging the smoothing condenser variable, output compensation for fluctuation in the source voltage can easily be conducted.
According to another feature thereof, the invention includes a load circuit having a discharge lamp, an inductance and a capacitance; and a combination-type high frequency inverter having a full-wave rectifier for rectifying a low frequency AC voltage without smoothing the voltage, a series circuit consisting of an inductor and a first switching means that is connected to a point between DC output terminals of said full-wave rectifier and has a function of an antiparallel diode, a series circuit consisting of a smoothing condenser, said first switching means, which is connected to a point between the DC output terminals of the full-wave rectifier, and a second switching means which has a function of an antiparallel diode and is adapted to be switched alternately with the first switching means, and a resonance condenser adapted to generate high frequency resonance with the inductor, said combination-type high frequency inverter adapted to operate in such a manner that the xe2x80x98onxe2x80x99 duration of the first switching means is variable, while the xe2x80x98onxe2x80x99 duration of the second switching means is fixed, and the combination-type high frequency inverter having a function of an active filter and serving to energize the load circuit with a high frequency output.
By operating the combination-type high frequency inverter that has a function of an active filter of a polarity reversing type with the xe2x80x98onxe2x80x99 duration of the switching means that is adapted to take part in charging the smoothing condenser being variable and the xe2x80x98onxe2x80x99 duration of the switching means that is adapted to take part in discharge from the smoothing condenser being fixed, the charge voltage on the smoothing condenser can be adjusted so that the high frequency output voltage and, consequently, the load characteristics are changed as desired. The invention described above is thus capable of easily giving a discharge lamp load characteristics that are optimal for the current mode in accordance with whether the discharge lamp is in the start-up mode or luminance mode. Furthermore, by making the xe2x80x98onxe2x80x99 duration of the switching means that is adapted to take part in charging the smoothing condenser variable, output compensation for fluctuation in the source voltage can easily be conducted.
According to yet another feature thereof, the invention includes a load circuit having a discharge lamp, an inductance and a capacitance; and a combination-type high frequency inverter having a full-wave rectifier for rectifying a low frequency AC voltage without smoothing the voltage, a series circuit consisting of a first switching means and a second switching means that are connected to a point between DC output terminals of said full-wave rectifier and are adapted to be alternately switched so as to have a function of an antiparallel diode, a series circuit consisting of an inductor and a smoothing condenser, said inductor connected in parallel with the second switching means, and a resonance condenser adapted to generate high frequency resonance with the inductor, said combination-type high frequency inverter adapted to operate in such a manner that the xe2x80x98onxe2x80x99 duration of the first switching means is variable, while the xe2x80x98onxe2x80x99 duration of the second switching means is fixed, and the combination-type high frequency inverter having a function of an active filter and serving to energize the load circuit with a high frequency output.
By operating the combination-type high frequency inverter that has a function of an active filter of a voltage reducing type with the xe2x80x98onxe2x80x99 duration of the switching means that is adapted to take part in charging the smoothing condenser being variable and the xe2x80x98onxe2x80x99 duration of the switching means that is adapted to take part in discharge from the smoothing condenser being fixed, the charge voltage on the smoothing condenser can be adjusted so that the high frequency output voltage and, consequently, the load characteristics are changed as desired. The invention described above is thus capable of easily giving a discharge lamp load characteristics that are optimal for the current mode in accordance with whether the discharge lamp is in the start-up mode or luminance mode. Furthermore, by making the xe2x80x98onxe2x80x99 duration of the switching means that is adapted to take part in charging the smoothing condenser variable, output compensation for fluctuation in the source voltage can easily be conducted.
According to yet another feature thereof, the invention includes a load circuit having a discharge lamp, an inductance and a capacitance; and a combination-type high frequency inverter having a full-wave rectifier for rectifying a low frequency AC voltage without smoothing the voltage, a series circuit consisting of an inductor that is connected to a point between DC output terminals of said full-wave rectifier and a first switching means having a function of an antiparallel diode, a series circuit consisting of a smoothing condenser and a second switching means which has a function of an antiparallel diode connected in parallel with the first switching means and is adapted to be switched alternately with the first switching means, and a resonance condenser adapted to generate high frequency resonance with the inductor, said combination-type high frequency inverter adapted to operate in such a manner that the xe2x80x98onxe2x80x99 duration of the first switching means is variable, while the xe2x80x98onxe2x80x99 duration of the second switching means is fixed, and the combination-type high frequency inverter having a function of an active filter and serving to energize the load circuit with a high frequency output.
By operating the combination-type high frequency inverter that has a function of an active filter of a boosting type with the xe2x80x98onxe2x80x99 duration of the switching means that is adapted to take part in charging the smoothing condenser being variable and the xe2x80x98onxe2x80x99 duration of the switching means that is adapted to take part in discharge from the smoothing condenser being fixed, the charge voltage on the smoothing condenser can be adjusted so that the high frequency output voltage and, consequently, the load characteristics are changed as desired. The invention described above is thus capable of easily giving a discharge lamp load characteristics that are optimal for the current mode in accordance with whether the discharge lamp is in the start-up mode or luminance mode. Furthermore, by making the xe2x80x98onxe2x80x99 duration of the switching means that is adapted to take part in charging the smoothing condenser variable, output compensation for fluctuation in the source voltage can easily be conducted.
According to yet another feature thereof, the invention includes a load circuit provided with a discharge lamp, an inductance and a capacitance and having an natural resonance frequency; and a combination-type high frequency inverter having a full-wave rectifier for rectifying a low frequency AC voltage without smoothing the voltage, at least a pair of switching means which have a function of an antiparallel diode and are adapted to be alternately switched, an inductor, a smoothing condenser, and a resonance condenser, said combination-type high frequency inverter adapted to operate with the duration of the xe2x80x98onxe2x80x99 state of one of the switching means variable and the xe2x80x98onxe2x80x99 duration of the other switching means fixed at a length of time where the range is 1 to 1.5 times the natural resonance cycle of the load circuit, and the combination-type high frequency inverter having a function of an active filter and serving to energize the load circuit with a high frequency output.
With the configuration as above, lagging switching is conducted with the combination-type high frequency inverter with the xe2x80x98onxe2x80x99 duration of one of the switching means fixed at a length of time where the range is 1 to 1.5 times the natural resonance cycle of the load circuit, there by preventing occurrence of phase advancing switching, which may otherwise exert an unfavorable influence on the switching means. By making the xe2x80x98onxe2x80x99 duration of the other switching means variable, the charge voltage on the smoothing condenser can be adjusted so that the high frequency output voltage and, consequently, the load characteristics are changed as desired. The configuration described above is thus capable of easily giving a discharge lamp load characteristics that are optimal for the current mode in accordance with whether the discharge lamp is in the start-up mode or luminance mode.
According to yet another feature thereof, the invention includes a load circuit provided with a discharge lamp, an inductance and a capacitance and having an natural resonance frequency; and a combination-type high frequency inverter having a full-wave rectifier for rectifying a low frequency AC voltage without smoothing the voltage, a series circuit consisting of an inductor and a first switching means that is connected to a point between DC output terminals of said full-wave rectifier and has a function of an antiparallel diode, a series circuit consisting of a smoothing condenser, said first switching means, which is connected to a point between the DC output terminals of the full-wave rectifier, and a second switching means which has a function of an antiparallel diode and is adapted to be switched alternately with the first switching means, and a resonance condenser adapted to generate high frequency resonance with the inductor, said combination-type high frequency inverter adapted to operate with the duration of the xe2x80x98onxe2x80x99 state of either the first switching means or the second switching means variable and the xe2x80x98onxe2x80x99 duration of the other switching means fixed at a length of time where the range is 1 to 1.5 times the natural resonance cycle of the load circuit, and the combination-type high frequency inverter having a function of an active filter and serving to energize the load circuit with a high frequency output.
With the configuration as above, lagging switching is conducted with the xe2x80x98onxe2x80x99 duration of one of the switching means of the combination-type high frequency inverter that has a function of an active filter of a polarity reversing type fixed at a length of time where the range is 1 to 1.5 times the natural resonance cycle of the load circuit, thereby preventing occurrence of phase advancing switching, which may otherwise exert an unfavorable influence on the switching means. By making the xe2x80x98onxe2x80x99 duration of the other switching means variable, the charge voltage on the smoothing condenser can be adjusted so that the high frequency output voltage and, consequently, the load characteristics are changed as desired. The configuration described above is thus capable of easily giving a discharge lamp load characteristics that are optimal for the current mode in accordance with whether the discharge lamp is in the start-up mode or luminance mode.
According to yet another feature thereof, the invention includes a load circuit provided with a discharge lamp, an inductance and a capacitance and having an natural resonance frequency; and a combination-type high frequency inverter having a full-wave rectifier for rectifying a low frequency AC voltage without smoothing the voltage, a series circuit consisting of a first switching means and a second switching means that are connected to a point between DC output terminals of said full-wave rectifier, have a function of an antiparallel diode and are adapted to be alternately switched, a series circuit consisting of an inductor and a smoothing condenser, said inductor connected in parallel with the second switching means, and a resonance condenser adapted to generate high frequency resonance with the inductor, said combination-type high frequency inverter adapted to operate with the duration of the xe2x80x98onxe2x80x99 state of either the first switching means or the second switching means variable and the xe2x80x98onxe2x80x99 duration of the other switching means fixed at a length of time where the range is 1 to 1.5 times the natural resonance cycle of the load circuit, and the combination-type high frequency inverter having a function of an active filter and serving to energize the load circuit with a high frequency output.
With the configuration as above, lagging switching is conducted with the xe2x80x98onxe2x80x99 duration of one of the switching means of the combination-type high frequency inverter that has a function of an active filter of a voltage reducing type fixed at a length of time where the range is 1 to 1.5 times the natural resonance cycle of the load circuit, thereby preventing occurrence of phase advancing switching, which may otherwise exert an unfavorable influence on the switching means. By making the xe2x80x98onxe2x80x99 duration of the other switching means variable, the charge voltage on the smoothing condenser can be adjusted so that the high frequency output voltage and, consequently, the load characteristics are changed as desired. The configuration described above is thus capable of easily giving a discharge lamp load characteristics that are optimal for the current mode in accordance with whether the discharge lamp is in the start-up mode or luminance mode.
According to yet another feature thereof, the invention includes a load circuit provided with a discharge lamp, an inductance and a capacitance and having an natural resonance frequency; and a combination-type high frequency inverter having a full-wave rectifier for rectifying a low frequency AC voltage without smoothing the voltage, a series circuit consisting of an inductor that is connected to a point between DC output terminals of said full-wave rectifier and a first switching means having a function of an antiparallel diode, a series circuit consisting of a smoothing condenser and a second switching means which has a function of an antiparallel diode connected in parallel with the first switching means and is adapted to be switched alternately with the first switching means, and a resonance condenser adapted to generate high frequency resonance with the inductor, said combination-type high frequency inverter adapted to operate with the duration of the xe2x80x98onxe2x80x99 state of either the first switching means or the second switching means variable and the xe2x80x98onxe2x80x99 duration of the other switching means fixed at a length of time where the range is 1 to 1.5 times the natural resonance cycle of the load circuit, and the combination-type high frequency inverter having a function of an active filter and serving to energize the load circuit with a high frequency output.
With the configuration as above, lagging switching is conducted with the xe2x80x98onxe2x80x99 duration of one of the switching means of the combination-type high frequency inverter that has a function of an active filter of a boosting type fixed at a length of time where the range is 1 to 1.5 times the natural resonance cycle of the load circuit, there by preventing occurrence of phase advancing switching, which may otherwise exert an unfavorable influence on the switching means. By making the xe2x80x98onxe2x80x99 duration of the other switching means variable, the charge voltage on the smoothing condenser can be adjusted so that the high frequency output voltage and, consequently, the load characteristics are changed as desired. The configuration described above is thus capable of easily giving a discharge lamp load characteristics that are optimal for the current mode in accordance with whether the discharge lamp is in the start-up mode or luminance mode.
According to yet another feature of the invention, the operating frequency of the combination-type high frequency inverter is set such that the operating frequency for the period when the discharge lamp is in the start-up mode is close to the natural resonance frequency of the load circuit so as to obtain such load characteristics as a high release voltage and a small amount of short-circuit current and that the operating frequency for the period when the discharge lamp is lit is sufficiently lower than the natural resonance frequency of the load circuit so as to obtain such load characteristics as a low release voltage and a great amount of short-circuit current.
Setting the operating frequency of the combination-type high frequency inverter at a value close to the natural resonance frequency of the load circuit accelerates start up of a discharge lamp, because resonance produces a high release voltage, while the high operating frequency produces a great inductance in the load circuit, resulting in such load characteristics as a small amount of short-circuit current. When the discharge lamp is in the lit state, resonance of the load circuit can be almost entirely prevented by controlling the operating frequency of the combination-type high frequency inverter to a level substantially lower than the natural resonance frequency of the load circuit. As a result, the inductance of the load circuit functions merely as an impedance and reduces the release voltage of the combination-type high frequency inverter, thereby turning off the discharge lamp or reducing its luminance in case the discharge lamp is close to the end of its life.
According to yet another feature thereof, the invention includes a body of a lighting system, and a discharge lamp lighting device supported by said body of the lighting system.